Stuffing box assembly

ABSTRACT

A stuffing box assembly ( 4 ) comprising a primary housing ( 8 ) having a longitudinally oriented hollow bore ( 11 ) extending therethrough, a hanger assembly ( 9 ) within the longitudinally oriented hollow bore of the primary housing, and drive means ( 10 ) received within the hollow bore of the hanger assembly. The hanger assembly has a longitudinally oriented hollow bore extending therethrough. The drive means has means ( 15 ) to releasably secure the drive means to a pump rod such that the pump rod is hung from and supported within the primary housing by the hanger assembly. Rotation of the drive means causes a corresponding rotation of the pump rod. The hanger assembly includes one or more seals ( 17 ) to contain well fluids and to help prevent the flow of well fluids into the bore of the hanger assembly.

FIELD OF THE INVENTION

This invention relates generally to oil well production equipment, andmore particularly to a new and useful stuffing box assembly for use onan oil or other well driven into an underground formation.

BACKGROUND OF THE INVENTION

When pumping oil (or for that matter water or other fluids) fromunderground formations, typically a downhole pump is utilized whereinthe pump is physically located deep within the well and used to pump theoil or fluid to the surface. In many such applications the downhole pumpof choice is a screw or progressive cavity pump. Screw or progressivecavity pumps generally operate through the revolution of a pump rotorwithin a stator. A rotating pump rod extends from the surface to thedownhole pump and is used to drive or rotate the rotor. A power supply,which most commonly would be comprised of a gas, diesel, hydraulic orelectric motor, provides the means to rotate the pump rod, and hence thepump rotor. A series of seals are used to engage the rotating pump rodat or near the point where it exits the top of the well to preventdownhole fluids from leaking into the environment. Traditionally theseseals and their related structural components have been referred to as astuffing box.

In older reciprocating-type wells, a single stationary stuffing box wastypically provided. In such applications packing material would normallybe inserted into the stuffing box and compressed against a dedicatedportion of the pump rod (that may be polished to present a smoothsealing surface) in order to minimize the leakage of well fluids. Withthe introduction of rotary or progressive cavity pumps, others havesuggested the use of a rotating stuffing box as a means to help guardagainst a premature failure of packing material that can sometimes occurwhen using a more traditional stuffing box in a rotary pump application(for example see Canadian patent 2,095,937 issued Dec. 22, 1998). Suchrotary stuffing boxes commonly employ a rotating or hollow shaftstructure that is received about the pump rod such that the hollow shaftrotates in unison with the pump rod. The exterior portion of the hollowshaft can be hardened and machined to provide a smooth surface againstwhich one or more seals act in order to help prevent leakage of fluidfrom the well. While these hollow shaft structures can be effective,they also add to the complexity of the stuffing box, its costs andweight.

In addition to stuffing boxes, the wellhead equipment on most oil wellsincludes a blowout preventer that may be used to seal around the pumprod in order to contain well fluids and maintain well control,particularly when pumping ceases. Blowout preventers have been producedin a wide variety of different configurations and, using an equally widevariety of different mechanical structures. Most commonly, blowoutpreventers are comprised of a pair of radially opposed rams havingsealing surfaces on their inner ends such that when the rams are driveninwardly toward the pump rod they sealingly engage the exterior of therod surface, thereby preventing the escape of fluids from the well. Insome instances the blowout preventer, rams may include gripping insertsor gripping surfaces that serve the further function of engaging thesurface of the pump rod to a degree that allows the rams to securelyhold and retain the pump rod in place.

The surface equipment on an oil well will often include a number ofadditional components, such as casing heads, tubing string hangers,tubing string rotators, flow-tees, backspin inhibiting devices, driveheads etc. In many applications it is also necessary to employ some formof pump rod hanging device that serves the function of accepting thevertical load of the pump rod (which in deep wells can be significant)and transmitting that load to the well casing. Often the pump rodhanging device takes the form of a rod clamp that is secured orcompressed about the exterior surface of the pump rod, typically at thetop or upper end of the rod. Pump rod clamps are commonly designed tofit or mate within correspondingly shaped recesses in a drive gear orequivalent structures, such that rotation of the drive gear causesrotational movement of the rod clamp and thus the pump rod.

As a result of the need for a substantial number of mechanicalcomponents at the surface of an oil well, the height of the wellheadequipment can often become significant. As the height of the surfaceequipment (sometimes referred to as a Christmas tree) increases, so doesits weight and the general necessity for larger and stronger flanges,bolts, threads and other such means that are used to hold adjacentcomponents together. The height and weight of the wellhead components iseven more significant where the well is not vertical, in which case theassembled equipment must be capable of accommodating the resultingbending moment. There is thus a desirability to minimize the height ofsurface production equipment that extends out of the ground above thewell casing. There is also the need for the use of highly effectivestuffing boxes and sealing mechanisms, and the need to simplify themechanical systems that are utilized to hang and to rotate a pump rodwithin a well, and to seal against the rod when the pumping operationceases.

SUMMARY OF THE INVENTION

The invention therefore, in one of its aspects, provides a stuffing boxassembly that helps to address some of the deficiencies in currentlyavailable wellhead equipment. The stuffing box is contained within ahousing that provides an effective means to seal against the pump ordrive rod, and that contains a pump rod hanger with related bearingcomponents and a mechanism that presents a simplified mechanicalstructure for driving the pump rod. In one embodiment the stuffing boxmay also contain an integrated blow out preventer. The invention alsoconcerns a new and novel casing head.

Accordingly, in one of its aspects the invention provides a stuffing boxassembly comprising a primary housing having a longitudinally orientedhollow bore extending therethrough; a hanger assembly within saidlongitudinally oriented hollow bore of said primary housing, said hangerassembly having a longitudinally oriented hollow bore extendingtherethrough; and, drive means received within said hollow bore of saidhanger assembly, said drive means having means to releasably secure saiddrive means to a pump rod such that the pump rod is hung from andsupported within said primary housing by said hanger assembly and suchthat rotation of said drive means causes a corresponding rotation of thepump rod, said hanger assembly including one or more seals to containwell fluids and to help prevent the flow of well fluids into said boreof said hanger assembly.

In a further aspect the invention provides a casing head for securing tothe upper end of the casing of a well extending into an undergroundformation, the casing head including one or more side entry passagewaysto permit the introduction of coiled tubing or other tubular or elongatemember into the wellbore of the casing without the removal of wellheadequipment positioned above said casing head.

In yet a further aspect the invention concerns a stuffing box assemblycomprising a primary housing; a removable hanger assembly releasably andsealingly receivable within a longitudinally oriented hollow boreextending through said primary housing, said hanger assembly having alongitudinally oriented hollow bore extending therethrough; and, drivemeans sealingly receivable within said hanger assembly and extendingthrough said hollow bore within said primary housing when said hangerassembly is received therein, said drive means including torque inputmeans permitting for the transference of rotational torque from a powersource to said drive means, said drive means having means to releasablysecure said drive means to a pump rod such that rotation of said drivemeans causes a corresponding rotation of the pump rod when securedthereto, said drive means including one or more seals between said drivemeans and the pump rod, when said hanger assembly is received withinsaid primary housing said hanger assembly hanging said drive means, anda pump rod when attached thereto, from said primary housing, said hangerassembly including bearings to facilitate the rotation of said drivemeans, said hanger assembly including one or more seals to seal againstthe exterior surface of said drive means to help prevent the flow offluid between said drive means and said hanger assembly.

In still a further aspect the invention provides a stuffing box assemblycomprising a primary housing; a hanger assembly within a longitudinallyoriented bore extending through said primary housing, said hangerassembly having a longitudinally oriented bore extending therethrough;and, drive means sealingly received within said hollow bore of saidhanger assembly, said drive means including torque input meanspermitting for the transference of rotational torque from a power sourceto said drive means, said drive means having means to releasably securesaid drive means to a pump rod such that rotation of said drive meanscauses a corresponding rotation of the pump rod when secured thereto,said hanger assembly hanging said drive means, and a pump rod whenattached thereto, from said primary housing, said hanger assemblyincluding bearings to facilitate the rotation of said drive means, saidhanger assembly including one or more seals to contain well fluids andto help prevent the flow of well fluid into said bore in said hangerassembly.

Further aspects and advantages of the invention will become apparentfrom the following description taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show moreclearly how it may be carried into effect, reference will now be made,by way of example, to the accompanying drawings which show the preferredembodiments of the present invention in which:

FIG. 1 is a vertical cross-sectional view through a typical oil wellthat employs a progressive cavity pump and having attached to thewellhead a stuffing box assembly generally constructed in accordancewith one of the preferred embodiments of the present invention;

FIG. 2 is a side elevational view of the stuffing box assembly shown inFIG. 1, having an electric drive motor attached thereto;

FIG. 3 is a side elevational view of the stuffing box assembly shown inFIG. 2, rotated 90°;

FIG. 4 is a cross-sectional view taken along the line of 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 3;

FIG. 6 is an exploded view of the stuffing box assembly (with a portionof its outer housing removed) shown in FIG. 2;

FIG. 7 is an enlarged detailed cross-sectional view taken along the line7-7 of FIG. 6;

FIG. 8 is a vertical cross-sectional view of an alternate embodiment ofthe stuffing box assembly of the current invention having mountedthereon an electric motor;

FIG. 9 is an exploded view of the stuffing box assembly shown in FIG. 8;

FIG. 10 is an enlarged detailed cross-sectional view taken along theline 10-10 of FIG. 9;

FIG. 11 is a vertical cross-sectional view of one embodiment of thestuffing box assembly in accordance with the present invention shown inassociation with an electric motor and a casing head, and furtherincluding a separate scrap view of the tubing (with a tubing rotatorattached thereto) and the stuffing box assembly (with a rod assembly)shown removed from the vertical cross-sectional view;

FIG. 12 is an enlarged view of the stuffing box assembly and casing headshown in FIG. 11 having the electric motor removed;

FIG. 13 is an upper side perspective view of the casing head shown inFIG. 12;

FIG. 14 is a side elevational view of the casing head shown in FIG. 13;

FIG. 15 is a sectional view taken along the line 15-15 in FIG. 14;

FIGS. 16 and 16A are vertical cross-sectional views of an alternateembodiment of the stuffing box assembly of the current invention havingmounted thereon an electric motor;

FIGS. 17 and 17A are vertical cross-sectional views of a furtheralternate embodiment to that shown in FIG. 16;

FIG. 18 is a vertical cross-sectional view of a further embodiment tothat shown in FIG. 17;

FIG. 19A is a further alternate embodiment to that shown in FIG. 18; and

FIG. 19B is a cross-sectional view taken along the line of 19B-19B inFIG. 19.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention may be embodied in a number of different forms.However, the specification and drawings that follow describe anddisclose only some of the specific forms of the invention and are notintended to limit the scope of the invention as defined in the claimsthat follow herein.

With reference to FIG. 1 there is shown in vertical cross section atypical oil well 1 that employs a progressive cavity pump 2 to lift oilto the surface. At the surface of the oil well the wellhead 3 hasattached to it a stuffing box assembly 4 constructed in accordance withone of the preferred embodiments of the present invention. In theembodiment of the well shown in FIG. 1, an electric or hydraulic motor 5provides the means by which a pump rod 6 is rotated in order to turn therotor 7 of the progressive cavity pump. In this embodiment motor 5 is ina direct drive configuration with rotor 7.

Turning next to FIGS. 2 through 7, there is shown from various anglesand with various degrees of cross sectioning the internal and externalfeatures and components of stuffing box assembly 4. As will beappreciated from an examination of those Figures, stuffing box 4 iscomprised generally of a primary housing 8, a hanger assembly 9 (that inthis embodiment is shown as being removable but that also may bepermanently fixed to housing 8), and a drive means 10 (that in thisembodiment is a drive rod but that, as discussed below, may also be arotating mandrel). Primary housing 8 has a longitudinally orientedhollow bore 11 extending generally through its middle portion into whichhanger assembly 9 is releasably receivable. As shown, hanger assembly 9also has a longitudinally oriented bore 12 extending therethrough thatis capable of sealingly receiving drive rod 10. Drive rod 10 is anelongate member that, when received within hanger assembly 9 with thehanger assembly situated within hollow bore 11 of primary housing 8,will preferably extend through the bottom of the primary housing. Driverod 10 further has an upper end 13 and a lower end 14, with lower end 14having means 15 thereon to releasably secure the drive rod to a pump rodsuch that rotation of the drive rod will cause a corresponding rotationof the pump rod. It will be appreciated that means 15 could be any oneof a variety of different mechanisms that could be used to secure thedrive rod to the pump rod, however, in most instances it is expectedthat means 15 will be a threaded connection that allows the two rods tobe threaded together.

Hanger assembly 9 is designed and configured to hang drive rod 10, and apump rod that may be attached thereto, from primary housing 8 when thehanger assembly is received within the primary housing. In order tofacilitate the rotation of the drive rod and pump rod, the hangerassembly preferably includes bearings 16 as well as one or more seals 17that seal against the exterior surface of the drive rod to prevent theflow of fluid between the drive rod and the hanger assembly. To helpfacilitate the seal between drive rod 10 and seals 17, the surface ofthe drive rod adjacent the seals may be polished or may have a smoothceramic or other coating applied. Polishing or coating the rod not onlyhelps to enhance the seal between the rod and seals 17 but alsopotentially extends the useful life of the rod.

In the embodiment of the hanger assembly shown in FIG. 7, bearings 16include an upper bearing 32, a middle bearing 33 and a lower bearing 34.It will be understood that other configurations of bearings could alsobe used and that the various bearings generally accommodate thrustand/or rotary loads. It will also be apparent that the hanger assemblyin this embodiment is manufactured in two primary sections; namely, abottom portion 35 and a lock down nut 36 that are threaded together oncethe various bearings and seals have been put in place. A cap 43 may bescrewed or bolted to the lock down nut and/or the bottom portion. Theupper portion of the hanger assembly may include a grease nipple orlubrication port 37 to permit the introduction of grease or lubricantsinto the hanger assembly to help lubricate the various bearings andseals. In addition to seals 17 positioned in the lower portion of thehanger assembly to seal against the drive rod and maintain well control(two of which are shown, however, more or fewer of which may beutilized), the hanger assembly may also include an upper seal 38 to sealbetween the upper or top portion of the hanger assembly and the topportion of the drive rod. When received within the primary housing,hanger assembly 9 will be static while permitting drive rod 10 to berotated. Accordingly, seals 17 and 38 are preferably dynamic seals thatseal against the rotating exterior surface of the drive rod when it isreceived within the hanger assembly. A series of static seals 39 areused to seal the hanger assembly with housing 8 and to seal lock downnut 36 within bottom portion 35.

While hanger assembly 9 may be hung within hollow bore 11 of primaryhousing 8 in a number of different manners, in the embodiment shown inthe attached drawings longitudinally oriented hollow bore 11 through theprimary housing includes a first diameter portion 18 at its upper end inorder to receive the hanger assembly and a second or lower, reduceddiameter, portion 19. In this embodiment the first and second diameterportions 18 and 19 are connected by a sloped shoulder portion 20 thatacts as a bearing surface against which a sloped exterior portion 21 ofhanger assembly 9 bears when the hanger assembly is received withinhollow bore 11 of the primary housing. The engagement of the slopedexterior surface 21 of the hanger assembly with the sloped shoulder 20of hollow bore 11 results in a friction fit between the hanger assemblyand the primary housing that securely and statically holds the hangerassembly within the housing such that the weight of the drive rod, andthe pump rod attached thereto, that is borne by the hanger assembly istransmitted, via the sloped shoulder contact, to the body of the primaryhousing. One or more of the static seals 39 (see FIG. 7) are preferablyplaced between the exterior surface of the hanger assembly and theinterior of hollow bore 11 of the primary housing in order to helpprevent the flow of fluid between the primary housing and the hangerassembly. The hanger assembly may also include one or more lock pins toprevent the hanger assembly (and hence the drive rod) from rotatingand/or lifting with primary housing 8, particularly in the event of apower loss, pump shut down or in a high pressure well. In a furtherembodiment sloped shoulder portion 20 could be a square or other shapedshoulder. It will also be appreciated that there could exist teeth,splines or other structures between the hanger assembly and the primaryhousing to prevent the hanger assembly from rotating. Alternately, thehanger assembly could be prevented from rotating by frictionalengagement with the primary housing.

In the embodiment of the invention shown, stuffing box assembly 4further includes a pair of radially opposed blowout preventer rams 23that are situated in transverse bores 24 that extend through the primaryhousing. Transverse bores 24 are in communication with the exterior ofthe housing and with hollow bore 11 such that when driven inwardlytowards the center of the housing, the blowout preventer rams sealinglyengage each other and the exterior surface of drive rod 10. It will beappreciated by those skilled in the art that the particular form of ramsused could vary from application to application. In most instances it isexpected that the interior surfaces of the rams will be fitted with aseal that generally has a shape that conforms to the exterior surface ofthe drive rod. When the rams are driven inwardly and compressed upagainst the surface of the drive rod the seals will pack off the openarea of the hollow bore in order to prevent the escape of well fluidspast the rams.

In some instances it may be desirable for the interior surfaces of therams to have gripping faces or, alternatively, gripping inserts (notshown) that can physically contact the exterior surface of the drive rodin order to securely hold it in place. The gripping faces or grippinginserts would typically be capable of holding both the vertical load ofthe drive rod and the pump rod attached thereto, as well as rotationaltorque that may be built up within the drive rod and pump rod on accountof either the operation of the compressive cavity pump or the tendencyfor the pump rod to exhibit back spin when the pumping operation ceasesand the weight of oil or fluid in the well bears directly upon the pumprotor. It will equally be appreciated that the blowout preventer ramswill, typically include various other features and elements that arecommonly used in blowout preventers, including ram stems and a mechanismto actuate the rams, whether it be through manually turning the stems orthrough the use of hydraulic, electric or pneumatic actuators.

As shown most clearly in FIGS. 2, 3 and 4, in one embodiment, stuffingbox assembly 4 includes one or more locking mechanisms 25 that assist inretaining hanger assembly 9 within hollow bore 11 of primary housing 8.In FIGS. 2, 3 and 4, the locking mechanisms are comprised of a pluralityof lock down or hold down screws 26 that are threadably received withinthe primary housing 8 of the stuffing box. Lock down screws 26 haveinterior ends that engage the exterior surface of hanger assembly 9 inorder to prevent the hanger assembly from being lifted within theprimary housing, particularly in the case of high pressure wells.Employment of lock down screws 26 maintains the seating of slopedexterior surface 21 of the hanger assembly with shoulder 20 of hollowbore 11, and in so doing also maintains the seating of seals 39 with theinterior surface of hollow bore 11 to prevent the leakage of well fluidsbetween the hanger assembly and the primary housing.

Rotational torque may be applied to drive rod 10 through the use of avariety of different mechanical and electro-mechanical means. Theexample of one of the preferred embodiments of the invention that isshown in the attached drawings is a direct drive system where drive rod10 is driven directly by electric or hydraulic motor 5. In this instancethe upper end of the drive rod includes a torque input means 27 thatpermits the transference of rotational torque from a drive source (inthis case motor 5) to the drive rod, which in turn transfers rotationaltorque to a pump rod attached thereto. While input means 27 could itselftake different forms, in the embodiment shown the input means comprisesa recess within the upper end of the drive rod which is of aconfiguration and size such that the recess accepts the end of the shaftof motor 5 when the motor is mounted on top of primary housing 8. Topermit the transference of rotational torque from the motor shaft to thedrive rod, the motor shaft may be splined with the recess and the driverod having a similar configuration or, alternatively, the motor may beequipped with a keyed shaft with the recess machined with an appropriatekey way. In any event, it will be appreciated that through mountingmotor 5 directly upon the upper surface of primary housing 8 such thatthe shaft of the motor is received within a corresponding configuredrecess in the upper end of drive rod 10, operation of motor 5 willresult in a direct rotation of the drive rod and the pump rod attachedthereto. It will also be appreciated that such a direct drive structurepresents a number of advantages, not the least of which includes a morecompact and simplified wellhead design, a more efficient drive structure(that eliminates the need for belts, chains, gears, pulleys etc.), theability to more accurately control the speed of rotation of the driverod and pump rod (particularly where a DC motor is utilized), asimplified structure that permits for the easy removal and replacementof the motor, a reduced wellhead height, and a mechanism by whichbackspin of the pump rod can be controlled and/or dissipated easily,economically and in a safe manner.

With reference to FIGS. 8, 9 and 10, there is disclosed therein anembodiment of stuffing box assembly 4 that includes means to pressurizethe interior of the stuffing box for purposes of helping to lubricateseals 17 and also, if desired, to help maintain the pressure within thestuffing box above wellbore pressure as a means to deter the influx ofwell fluids into the stuffing box. In this embodiment the shaft of motor5 includes a longitudinal hollow bore 28 that extends therethrough.Similarly, a longitudinally oriented hollow bore 29 extends through atleast the upper end of drive rod 10 such that when the shaft of themotor is received within input means 27 longitudinal bore 28 within themotor shaft is in fluid communication with longitudinal bore 29 of thedrive rod. As shown most clearly in FIG. 10, drive rod 10 is also formedwith at least one transverse oriented exit port 30 that extends from theexterior surface of the drive rod to bore 29 such that bore 29 iseffectively in fluid communication with the drive rods' exteriorsurface. Such a structure of hollow bores extending through the motorshaft and into the upper end of the drive rod, in combination with oneor more exit ports 30, permits bore 28 within the motor shaft to be atleast partially filed with oil and to have connected to, or associatedtherewith, a pressurization means to pressurize the oil. The pressurizedoil (or for that matter other lubricant) is forced through the motorshaft, into the bore in the upper end of the drive rod, through thetransverse passage, and into the interior of hanger assembly 9.Transverse exit ports 30 deliver pressurized oil to the exterior surfaceof the drive rod adjacent to, or in the general vicinity of, dynamicseals 17, thereby helping to lubricate the seals, pressurizing theinterior of the stuffing box, and helping to maintain well control bydeterring the influx of well fluids into the interior portions of thestuffing box. As mentioned, if desired the pressurization means can bedesigned so as to pressurize the oil or fluid injected into the stuffingbox to such a level that the pressure within the interior of hangerassembly 9 exceeds the pressure of the wellbore.

The source of pressurization used to pressurize the interior of thestuffing box could be an exterior source of pressurized fluid (such as ahydraulic pump or accumulator) that is piped or otherwise connected toone or the other of bores 28 and 29. In the embodiment shown in FIGS. 8,9, 10 the upper end of bore 28 within the motor shaft is sealed and apressurization piston 31 is received therein. Piston 31 may be eitherspring or gas actuated. Regardless, in either instance the piston exertsa compressive force upon the oil received within bore 28. If desired thesealing of the upper end of bore 28 within the motor shaft can beaccomplished through the use of a removable cap or nut 42 that permitsan increase in the compression of the spring 41 used to energize piston31. Alternately, when the piston is gas actuated a valve (such as asnifter valve) can be mounted in the top of the shaft to permit theaddition of further gas in order to more highly pressurize the pistonand thereby enhance or increase the pressurization of the oil withinbores 28 and 29. A removable cap at the top of bore 28 will also allowfor the level of oil within the bore to be checked periodically.

In an alternate embodiment to that as shown in FIGS. 8 and 10, anexternal source of pressurized oil or lubricant may be connected to alubrication port 37 to permit the introduction of lubricant into thehanger assembly in order to lubricate the various bearings and seals. Insuch an embodiment the drive rod and/or the hanger assembly may befitted with specialized lubrication ports to direct lubricant toparticular seals, bearings, or other areas where lubrication may bedesired. Whether it be through the use of a lubrication system such asthat shown in FIGS. 8, 9 and 10, or a separate stand-alone lubricationsystem connected to the hanger assembly, it is expected that duringoperation the lubricant will be pressurized to the point where it willslowly seep past dynamic seals 17 and leak into the well. This will helpto ensure that the seals are adequately lubricated, will assist influshing debris from the bearing and keeping the bearings free ofcontaminants, and will also help to prevent the ingress of well fluidsinto the stuffing box. In most instances it is expected that the leakageof lubricant into the well will be something in the range of a few cubiccentimeters per day, making the loss of lubricant negligible under thecircumstances.

In a further embodiment of the invention, stuffing box assembly 4includes a tubing hanger 44 that effectively hangs a tubing string 45from primary housing 8. The tubing hanger may be any one of a widevariety of commonly utilized tubing hangers that permit tubing to besecurely held within the wellhead while preventing the loss of fluidsbetween the hanger and the internal bore of housing 8. In the embodimentshown in FIG. 11, tubing string 45 has secured thereto a downhole tubingrotator 46, such as that shown and described in U.S. Pat. No. 7,306,031.It will be appreciated by those having a thorough understanding of theinvention that through permitting the incorporation of tubing hanger 44within stuffing box assembly box 4, the overall height of the wellheadcan be reduced; once again having associated beneficial effects.Furthermore, the utilization of a downhole rotator eliminates the needfor an external tubing rotator and further reduces the size and weightof the exterior wellhead components.

In the embodiment of the invention shown in FIGS. 1 and 11 through 15,stuffing box assembly 4 is mounted upon a unique and novel casing head47. In this embodiment the casing head contains one or more side entrypassageways 48. In the attached Figures two such side entry passagewaysare incorporated within the casing head. During normal pumpingoperations side entry passageways 48 would typically be closed offthrough the use of removable plugs 49. Alternately, valves could be usedin place of the plugs. Plugs 49 keep debris out of passageways 48 andalso maintain well control. However, if for any reason (for exampleformation stimulation purposes) it should become necessary to insertcoiled tubing or other tubular or elongate members into the well, plug49 can be removed from one of the side entry passageways permitting thecoiled tubing or other device to be inserted into the well without theneed to disassemble wellhead equipment and without the need to pull thetubing from the well. It will be appreciated that particularly where adownhole tubing rotator 46 is utilized, the advantage provided by casinghead 47 is significant in that it allows for the insertion of coiledtubing below the position of the tubing rotator. Otherwise, anyactivities requiring the insertion of coiled tubing or similar devicesinto the well would necessitate the removal of wellhead equipment, thepulling of the tubing string (at least to the point where the rotator isclear of the well head) and then the insertion of the coiled tubing, allof which increase costs and downtime of the well.

As shown in the attached Figures, in a preferred embodiment passageways48 are arranged with their longitudinal axes at a “shallow” anglerelative to the centre line of the wellhead to permit the coiled tubingor other tubular or elongate member to be inserted at a shallow angle ofapproach relative to the casing and any tubing string that may bereceived therein. In these regards, the “shallow” angle is preferablyless than 45°, more preferably less than 30° and most preferably lessthan 20°. That is, a shallow angle of approach between the passagewaysand the tubing string will allow the coiled tubing or other member to beinserted while minimizing the potential for damage to either the coiledtubing or the tubing string.

Casing head 47 may also be configured to accept the tubing string hanger44 or, alternately, and as shown in the attached Figures, the tubingstring hanger may be located in primary housing 8. Lock down or holddown screws for the tubing string hanger may be located in the upperflange of the casing head.

FIG. 16 shows an alternate embodiment of the invention to that showngenerally in FIGS. 8 through 10. In this embodiment, the drive means isnot a drive rod but is instead a rotating mandrel 51 through which thepump or polished rod 6 is received. In the embodiment depicted in FIG.16, the energy to drive the pump rod is provided by an electric orhydraulic motor 5 that is situated in a direct-drive configuration. Inthis particular embodiment the motor shaft 50 is preferably hollow (orat least the lower portion of it is preferably hollow) to be receivedabout the upper end of the pump rod 6 and into rotating mandrel 51. Adrive connection exists between the motor shaft 50 and the rotatingmandrel that permits the transference of rotational energy from themotor shaft to the mandrel. In most instances it is expected that thatdrive connection will be in a form of a series of splines 52 on themotor shaft and the rotating mandrel, wherein the splines mesh togetherin order to allow for the transference of rotational torque. In othercases keys, shaped shafts and other drive connection mechanisms couldequally be used in place of splines 52.

With reference once again to FIG. 16, it will be understood that whenthe pump rod extends through the hollow interior 53 of rotating mandrel51, it will be necessary to transfer rotational energy from the mandrelto the pump rod in order to cause the rod to rotate. In this embodimentof the invention, the preferred mechanism for doing so comprises slips54 that are inserted between the exterior surface of the pump rod andthe interior diameter of mandrel 51. As shown, the lower portion of thehollow interior 53 of rotating mandrel 51 preferably decreases indiameter forming a generally conical shape into which slips 54 arereceived. The weight of pump rod 6 bearing against slips 54 will thushave the tendency to enhance the grip between the slips, the pump rodand the interior surface of the mandrel, to the point where rotation ofthe mandrel by motor shaft 50 will cause the simultaneous rotation ofpump rod 6. In this manner the motor shaft, rotating mandrel and pumprod will all rotate in unison, effectively as a single component. Staticseals 55 (for example o-rings) are preferably inserted between thebottom portion of the rotating mandrel and the pump rod to prevent theinflux of well fluids into hollow interior 53. Otherwise, rotatingmandrel 51 generally functions in a similar fashion to drive rod 10 inthat it transfers the load of the pump rod onto thrust bearings withinthe hanger assembly with radial bearing facilitating the rotationalmovement of the mandrel.

A slightly different variation to the embodiment shown in FIG. 16 isdepicted in FIG. 17. The embodiment of FIG. 17 is overall generallysimilar to that shown in FIG. 16 with the primary exception being thatpump rod 6 is secured to rotating mandrel 51 through the use of a rodclamp 56 rather than slips 54. In this embodiment, rod clamp 56 has anoutside diameter that is smaller than the inside diameter of hollowmotor shaft 50 to allow the clamp to at least be partially receivedwithin the motor shaft. Rod clamp 56 will be securely held about theexterior surface of pump rod 6 (preferably through frictional engagementsuch as what would occur as a result of a conical shaped interior ofrotating mandrel 51 and elements on the rod clamp that are able todeflect inwardly towards a rod when wedged against the conical slopingshape of the mandrel). Mandrel 51 also preferably contains splines (ordrive dogs) 57 that transfer rotational movement of the mandrel to thepump rod. As shown in FIG. 17, in this variation the pump rod may alsoextend upwardly through the centre of motor 5.

The embodiment of the invention shown in FIG. 18 is yet a furtherversion of that shown in FIGS. 16 and 17. Here, the pump rod 6 is shownas extending through the motor 5 (as in FIG. 17), however, rod clamp 56is a more traditional polished rod clamp and it has been moved to aposition above the motor as is more common in current drive heads. Theweight of the pump rod is thus transferred from the rod to clamp 56, tomotor shaft 50, and then ultimately to rotating mandrel 51 which, as isin case of the previously described embodiments, engages both thrust andradial bearings within hanger assembly 9.

FIG. 19 shows yet a further possible embodiment of the invention to thatshown in FIGS. 16 through 18. Here the hollow motor shaft has a splinedconnection with a torque coupling 57 which transmits rotational torquefrom the motor shaft to rod clamp 56. Clamp 56 physically bears againstthe upper surface of rotating mandrel 51 and also contains in its lowerend a rotating sleeve 57 that rotates with rod clamp 56 and that issplined to mandrel 51. Accordingly, rotation of motor shaft 50 causestorque coupling 57, rod clamp 56, rotating sleeve 58, rotating mandrel51 and pump rod 6 to rotate in unison with the motor shaft. In thisembodiment motor 5 can be more easily removed from the wellhead.

From a thorough understanding of the invention described herein andshown in the attached drawings it will become clear that the stuffingbox assembly of the present invention presents a highly efficient,compact, structure that is capable of sealingly hanging a drive rod, anda pump rod attached thereto, within a well using a minimum number ofwell head components to reduce the overall height and weight of thewellhead. The design and structure of the stuffing box assembly and itsprimary housing allows for the integration of a blowout preventer/rodclamp within the same compact unit, thereby eliminating the need for aseparate BOP and rod clamp. A simplified manner of applying rotationaltorque to the drive and pump rods is also provided that allows for thedirect mounting of an electric or hydraulic motor on top of the stuffingbox, hence eliminating the need for more complex drive gear systems thatadd to the weight of the wellhead equipment, increase expense, and inmany instances provide off-balanced non-symmetrical loading of wellheadequipment. Where a hydraulic or DC motor is used to rotate the driverod, there is greater ability to control the rotational speed of thedrive and pump rods in a safe and inexpensive manner that can also beused to control back spin. As has also been described, the stuffing boxassembly of the present invention provides a manner to easily andeffectively pressurize the internal portion of the stuffing box in orderto lubricate and enhance the effectiveness and longevity of its bearingsand seals. The novel and unique casing head design of the inventionpresents a simple, fast and efficient means for coiled tubing to beinserted into the well without the need to disassemble wellheadcomponents and without the need for cranes or boom trucks to pull thetubing string.

It is to be understood that what has been described are the preferredembodiments of the invention and that it may be possible to makevariations to these embodiments while staying within the broad scope ofthe invention. Some of these variations have been discussed while otherswill be readily apparent to those skilled in the art. For example, whilethe invention has been described as used in association with a directdrive electric or hydraulic motor, it will be appreciated that the motorcould equally be off-set from the centerline of the stuffing box withthe rotation of the drive or pump rod accomplished through the use ofconventional pullies and gears.

1. A stuffing box assembly comprising: a primary housing having alongitudinally oriented hollow bore extending therethrough; a hangerassembly within said longitudinally oriented hollow bore of said primaryhousing, said hanger assembly having a longitudinally oriented hollowbore extending therethrough; and, drive means received within saidhollow bore of said hanger assembly, said drive means having means toreleasably secure said drive means to a pump rod such that the pump rodis hung from and supported within said primary housing by said hangerassembly and such that rotation of said drive means causes acorresponding rotation of the pump rod, said hanger assembly includingone or more seals to contain well fluids and to help prevent the flow ofwell fluids into said bore of said hanger assembly.
 2. The stuffing boxassembly as claimed in claim 1 wherein said hanger assembly includesbearings to facilitate the rotation of said drive means, said hangerassembly further including one or more seals to prevent the flow offluid between said hanger assembly and said primary housing.
 3. Thestuffing box assembly as claimed in claim 2 wherein said drive means isa drive rod.
 4. The stuffing box assembly as claimed in claim 3 furtherincluding a pair of radially opposed blowout preventer rams situated intransverse bores extending through said primary housing, said transversebores in communication with said longitudinal bore through said primaryhousing such that said blowout preventer rams sealingly engage theexterior surface of said drive rod when said rams are advanced withinsaid transverse bores toward said drive rod.
 5. The stuffing boxassembly as claimed in claim 2 wherein said longitudinally orientedhollow bore through said primary housing includes a first diameterportion and a second reduced diameter portion, said first and saidsecond diameter portions connected by a shoulder portion, said shoulderportion acting as a bearing surface against which said hanger assemblyis engaged, said shoulder portion bearing the weight of said hangerassembly, said drive means and a pump rod when attached thereto.
 6. Thestuffing box assembly as claimed in claim 2 wherein said primary housingincludes one or more locking mechanisms to retain said hanger assemblywithin said primary housing.
 7. The stuffing box assembly as claimed inclaim 6 wherein said one or more locking mechanisms comprise one or morelock down screws.
 8. The stuffing box assembly as claimed in claim 2wherein said drive means includes torque input means permitting for thetransference of rotational torque from a power source to said drivemeans and to a pump rod attached thereto.
 9. The stuffing box assemblyas claimed in claim 8 wherein said torque input means comprises a recessin the upper end of said drive means and said power source comprises anelectric or hydraulic motor, said recess configured and sized to acceptthe shaft of said electric or hydraulic motor such that the operation ofsaid motor causes a direct rotation of said drive means.
 10. Thestuffing box assembly as claimed in claim 2 wherein said drive meanscomprises a rotatable mandrel.
 11. The stuffing box assembly claimed inclaim 10 wherein said hanger assembly is hung and supported within thelongitudinally oriented hollow bore of said primary housing by ashoulder portion on said primary housing.
 12. The stuffing box assemblyis claimed in claim 11 wherein said rotatable mandrel has alongitudinally oriented hollow bore for receiving a pump rod therethrough.
 13. The stuffing box assembly as claimed in claim 12 wherein,the hollow bore through said rotatable mandrel has a reduced diameterportion, said mandrel including slips to engage a pump rod receivedthrough said hollow bore in said mandrel, said slips engaging the pumprod at said reduced diameter portion in order to hang the pump rod fromsaid mandrel such that rotation of said mandrel causes a simultaneousrotation of the pump rod.
 14. The stuffing box assembly as claimed inclaim 12 including a rod clamp, said rod clamp operatively securing thepump rod to said rotatable mandrel such that rotation of said mandrelcauses a corresponding rotation of the pump rod, said rod clamp furthertransferring the axial or longitudinal load of the pump rod to saidrotating mandrel.
 15. The stuffing box assembly as claimed in claim 9wherein said shaft of said motor includes a longitudinal hollow boreextending therethrough, when said shaft of said motor is received withinsaid recess in the upper end of said drive means said longitudinal borein said motor shaft is in fluid communication with a longitudinallyoriented hollow bore extending through at least the upper end of saiddrive means, said bore in said drive means having at least onetransverse oriented exit port in communication with the exterior surfaceof said drive means, said bore extending through said shaft of saidmotor being at least partially filled with lubricant and havingassociated therewith pressurization means to pressurize said lubricant,said pressurization means forcing said lubricant through said shaft ofsaid motor into said bore within the upper end of said drive means andthrough said transverse exit port, said lubricant assisting in thelubrication of said seals and pressurizing the interior of said stuffingbox.
 16. The stuffing box assembly as claimed in claim 15 wherein saidpressurization means pressurizes said lubricant to a level such that thelubricant pressure within said stuffing box exceeds the pressure offluids within a well upon which said stuffing box is mounted to helpprevent the flow of well fluids into said stuffing box.
 17. The stuffingbox assembly as claimed in claim 16 wherein the upper end of saidlongitudinal bore extending through said shaft of said electric orhydraulic motor is sealed, said pressurization means situated withinsaid longitudinal bore in said motor shaft.
 18. The stuffing boxassembly as claimed in claim 17 wherein said pressurization meanscomprises a spring or gas actuated piston.
 19. The stuffing box assemblyas claimed in claim 2 including an external source of pressurizedlubricant connected to the interior of said hanger assembly, saidpressurized lubricant lubricating said one or more seals andpressurizing said hanger assembly to a higher pressure than the pressureof a wellbore upon which said stuffing box is mounted to help preventthe flow of well, fluids into said hanger assembly.
 20. The stuffing boxassembly as claimed in claim 1 in combination with a casing head, saidcasing head including one or more side entry passageways to permit theintroduction of coiled tubing or other tubular or elongate member intothe wellbore of a wellhead onto which said stuffing box assembly ismounted, said introduction of said coiled tubing or other tubular orelongate member occurring at a point below said stuffing box assemblyand without the removal of said stuffing box assembly from the wellhead.21. A casing head for securing to the upper end of the casing of a wellextending into an underground formation, the casing head including oneor more side entry passageways to permit the introduction of coiledtubing or other tubular or elongate member into the wellbore of thecasing without the removal of wellhead equipment positioned above saidcasing head.
 22. The casing head as claimed in claim 21 includingremovable plugs in said one or more side entry passageways to helpprevent the ingress of debris into the wellbore and the escape of fluidsfrom the wellbore.
 23. The casing head as claimed in claim 22 whereinsaid one or more side entry passageways are arranged with theirlongitudinal axes at a shallow angle relative to the centerline of thewellhead to permit the coiled tubing or other tubular or elongate memberto be inserted at a shallow angle of approach relative to the casing andany tubing string that may be received therein.
 24. A stuffing boxassembly comprising: a primary housing; a removable hanger assemblyreleasably and sealingly receivable within a longitudinally orientedhollow bore extending through said primary housing, said hanger assemblyhaving a longitudinally oriented hollow bore extending therethrough;and, drive means sealingly receivable within said hanger assembly andextending through said hollow bore within said primary housing when saidhanger assembly is received therein, said drive means including torqueinput means permitting for the transference of rotational torque from apower source to said drive means, said drive means having means toreleasably secure said drive means to a pump rod such that rotation ofsaid drive means causes a corresponding rotation of the pump rod whensecured thereto, said drive means including one or more seals betweensaid drive means and the pump rod, when said hanger assembly is receivedwithin said primary housing said hanger assembly hanging said drivemeans, and a pump rod when attached thereto, from said primary housing,said hanger assembly including bearings to facilitate the rotation ofsaid drive means, said hanger assembly including one or more seals toseal against the exterior surface of said drive means to help preventthe flow of fluid between said drive means and said hanger assembly. 25.A stuffing box assembly comprising; a primary housing; a hanger assemblywithin a longitudinally oriented bore extending through said primaryhousing, said hanger assembly having a longitudinally oriented boreextending therethrough; and, drive means sealingly received within saidhollow bore of said hanger assembly, said drive means including torqueinput means permitting for the transference of rotational torque from apower source to said drive means, said drive means having means toreleasably secure said drive means to a pump rod such that rotation ofsaid drive means causes a corresponding rotation of the pump rod whensecured thereto, said hanger assembly hanging said drive means, and apump rod when attached thereto, from said primary housing, said hangerassembly including bearings to facilitate the rotation of said drivemeans, said hanger assembly including one or more seals to contain wellfluids and to help prevent the flow of well fluid into said bore in saidhanger assembly.
 26. The stuffing box assembly as claimed in claim 25wherein said drive means is a rotating mandrel, said rotating mandrelhaving a longitudinally oriented hollow bore for securedly receiving thepump rod therein such that rotation of the rotating mandrel causes acorresponding rotation of the pump rod.